As is known, there are a variety of types of magnetic field sensing elements, including, but not limited to, Hall effect elements, magnetoresistance elements, and magnetotransistors. As is also known, there are different types of Hall effect elements, for example, a planar Hall element, a vertical Hall element, and a circular Hall element. As is also known, there are different types of magnetoresistance elements, for example, a giant magnetoresistance (GMR) element, an anisotropic magnetoresistance element (AMR), a tunneling magnetoresistance (TMR) element, and a magnetic tunnel junction (MTJ).
Hall effect elements generate an output voltage proportional to a magnetic field. In contrast, magnetoresistance elements change resistance in proportion to a magnetic field. In a circuit, an electrical current can be directed through the magnetoresistance element, thereby generating a voltage output signal proportional to the magnetic field.
Magnetic field sensors, i.e., circuits that use magnetic field sensing elements, are used in a variety of applications, including, but not limited to, a current sensor that senses a magnetic field generated by a current carried by a current-carrying conductor, a magnetic switch that senses the proximity of a ferromagnetic object, a rotation detector that senses passing ferromagnetic articles, for example magnetic domains of a ring magnet, and a magnetic field sensor that senses a magnetic field density of a magnetic field.
As is known, some integrated circuits have internal built-in self-test (BIST) capabilities. A built-in self-test is a function that can verify all or a portion of the internal functionality of an integrated circuit. Some types of integrated circuits have built-in self-test circuits built directly onto the integrated circuit die. Typically, the built-in self-test is activated by external means, for example, a signal communicated from outside the integrated circuit to dedicated pins or ports on the integrated circuit. For example, an integrated circuit that has a memory portion can include a built-in self-test circuit, which can be activated by a self-test signal communicated from outside the integrated circuit. The built-in self-test circuit can test the memory portion of the integrated circuit in response to the self-test signal.
Conventional built-in self-test circuits tend not to allow the integrated circuit to perform its intended function while the built-in self-test is being performed. Instead, during the built-in self-test, the built-in self-test circuit exercises all of, or parts of, circuits on the integrated circuit in particular ways that do not necessarily allow concurrent operation of functions that the integrated circuit is intended to perform. Therefore, the built-in self-test is typically only activated one time, for example, upon power up of the integrated circuit, or from time to time. At other times, the built-in self-test circuit and function are dormant and the integrated circuit can perform its intended function.
Furthermore, when used in magnetic field sensors, conventional built-in self-test circuits tend not to test the magnetic field sensing element used in the magnetic field sensor.
It would be desirable to provide built in self-test circuits and techniques in a magnetic field sensor that allow the self-test to be run from time to time or upon command while the magnetic field sensor concurrently performs its intended function. It would also be desirable to provide such a concurrent self-test that tests a magnetic field sensing element used within the magnetic field sensor.